[LeetCode47]Permutations II

Given a collection of numbers that might contain duplicates, return all possible unique permutations.

For example,
[1,1,2] have the following unique permutations:
[1,1,2], [1,2,1], and [2,1,1].

Analysis:

similar with the former question permutations, here we need to sort the array, and check multiple numbers

Java

public class Solution {
    List<List<Integer>> result;
	 ArrayList<Integer> solu;
    public List<List<Integer>> permuteUnique(int[] num) {
        result = new ArrayList<>();
		 solu = new ArrayList<>();
		 int[] flag = new int[num.length];
		 Arrays.sort(num);
		 for(int i=0;i<flag.length;i++)
			 flag[i]=0;
		 genPermutation(0, num, flag);
		 return result;
    }
    public void genPermutation(int level, int[] num, int[] flag){
		 if(level == num.length){
			 result.add(new ArrayList<>(solu));
			 return;
		 }
		 for(int i=0;i<num.length;i++){
			 
			 if(flag[i]==0){
				 if(i>0 && num[i]==num[i-1] &&flag[i-1]==0)
					 continue;
				 flag[i] = 1;
				 solu.add(num[i]);
				 genPermutation(level+1, num, flag);
				 solu.remove(level);
				 flag[i] = 0;
			 }
		 }
	 }
}

c++

class Solution {
public:
    void GeneratePermuteUni(vector<vector<int>> &result,
                     vector<int> &solu,
                     int level,
                     vector<int> &visited,
                     vector<int> &num
                     ){
    if(level == num.size()){
        result.push_back(solu);
        return;
    }
    for(int i=0;i<num.size();i++){
        if(visited[i]==0){
            if(i>0 && num[i]==num[i-1] && visited[i-1]==0)
                continue;
            visited[i]=1;
            solu.push_back(num[i]);
            GeneratePermuteUni(result,solu,level+1,visited,num);
            solu.pop_back();
            visited[i]=0;
        }
    }
}
vector<vector<int> > permuteUnique(vector<int> &num) {
    vector<vector<int>> result;
    vector<int> solution;
    vector<int> visited(num.size(),0);
    if(num.size() == 0) return result;
    sort(num.begin(), num.end());
    GeneratePermuteUni(result,solution,0,visited,num);
    return result;
}
};